Key Takeaways -
- Tagging tables is crucial for PDF accessibility.
- Complex tables are more challenging to tag correctly.
- Merged cells and cross-page tables add complexity to the tagging process.
- Tables are read out like 3D structures by assistive technologies.
- Writing a table summary is made mandatory by WCAG.
One of the critical aspects of PDF accessibility is ensuring proper PDF tagging. The tags are hidden markups that provide a logical structure to the PDF content. When appropriately used, these markups optimize the reading experience through screen-readers and other assistive technology.
Efficiently tagging tables in PDF
Tables are one of the most challenging elements to tag effectively in a PDF document. Their complex nature makes it difficult to navigate with assistive technologies. Before moving into the tips for efficient tagging of PDF tables, let’s understand how a screen reader might read a table.
How screen readers read tables
Unlike most elements in a PDF, the screen readers read out tables like a 3-dimensional structure. The screen reader will first declare the size of the table, followed by the cell location, and continue to read the data cells, including what changed in the location and any row and column headers that did not apply to the last cell it read. In the case of a complex table with merged cells, the complicated reading order adds to the cognitive load of understanding the information.
Not all tabular elements are 'tables.'
All content with tabular formatting like – calendars, tables of content, forms, etc., should not be tagged as a table. The screen reader will read the table header before reading the content in table cells, leading to massive time consumption to find simple pieces of information.
Tips for tagging tables
After discussing how a screen reader interprets table tags and what is not a table, let’s take a look at efficient accessible table tips for the best reading experience. A table represents data in an organized and concise manner. Simple tables refer to tables with one column header and one row header designated for the data. Formatting the header row and column allows assistive technology to determine how to announce the data.
A table’s structure elements depend on the content of the table. Sometimes, the complex data leads to complex tables. One must avoid complex tables – they take considerable effort and time to tag correctly, and they are difficult for people using assistive technology to understand.
Table column and row headings should be tagged as ‘headings.’ This enables the screen readers to read the headers first, followed by table cells.
Links in the table cells should be tagged as ‘links’.
Blank cells or cells without any content can confuse screen readers. Ideally, it would be best if you avoided empty cells. In this case, the screen reader will announce the headers and have nothing to report about the blank cell. It is preferable to have the blank cell read as ‘blank cell’ or ‘intentionally blank’.
Merged cells are tricky for screen readers to read out and challenge the user to understand. They appear when there is more than one row or column header, and it would help if you used them only when necessary.
Sometimes tables are large and spill over more than one page, and it is critical to ensure the content is connected and tagged as one table.
WCAG mandates a table summary that provides vital information to the assistive technology user about the table’s structure. The table summary should include:
- A description.
- The number of row and column headers.
- Explanations of any merged cells or other structural abnormalities.
Tagging different table elements, despite their complex relationships, does not have to be complicated. You can quickly tag tables using PREP. PREP is a PDF remediation tool with sophisticated AI-powered auto-tag detection software that can quickly and efficiently tag tables. It can also handle complex elements like merged cells, cross-page tables, etc., and correctly tag them for an easy reading experience by assistive technology users.